Apparatus and process for imparting twist to filamentary material

ABSTRACT

A novel process and apparatus for twisting filamentary material such as yarn is disclosed wherein yarn is twisted down stream of a heating means and intermediate of take-up and feed stations. Opposite sides of the yarn are contacted at successive points therealong thus gripping the yarn while both an advancing and rolling motion is imparted thereto. Such motion is imparted to the yarn in one physical embodiment of the invention by means of a pair of rolls provided with meshed teeth formed along circumferential surfaces thereof. The rolls in such embodiment are mounted in angular relationship to each other so as to permit the teeth of respective rolls to engage opposite sides of a filamentary piece of material passing between said rolls at opposite sides and at successive points therealong. Such contact along successive opposite portions of the yarn causes the yarn to take a continuous and essentially stable path between the rolls and enables a positive grip to be imparted to the yarn thereby overcoming the torque imparted to the yarn as a frictional twist component of the meshed teeth. The apparatus of the present invention may thus be characterized as a friction twist head and its method of operation a process for imparting false twist to filamentary material by frictional contact.

United States Patent 11 1 Richter 1451 Oct. 22, 1974 1 1 APPARATUS AND PROCESS FOR IMPARTING TWIST TO FILAMENTARY MATERIAL [75] Inventor:

[52] US. Cl 57/77.4. 57/516, 57/156 [51] Int. Cl. D0lh 7/92, D02g 1/08, D02g 1/04 [58] Field of Search 57/773. 77.4, 77.42, 77.45,

[56] References Cited UNITED STATES PATENTS 2.262.589 11/1941 Peck 57/77.4 X 2.602.195 7/1952 Licbowitz 57/51.4 2.796.725 6/1957 Urrutia 57/51.4 2.939.269 6/1960 Dobson 57/77.4 2,943,433 7/1960 Van Dijk 57/77.42 X 3.112.600 12/1963 Stoddard ct a1. 57/774 X 3.156.084 11/1964 Van Dijk 57/77.4 3.373.554 3/1968 Raschlc 57/77.4 3,394,540 7/1968 Bentov 57/77.4 X 3.488.941 1/1971) Asaka 57/77.4 X 3.659.408 5/1972 Burr 57/77.4 X

FORElGN PATENTS 0R APPLlCATlONS 351,100 6/1931 Great Britain 57/77.42

480,796 3/1953 Italy 57/77.4 1.242.321 6/1967 Germany 57/774 Primary Examiner.lohn W, Huckert Assistant ExaminerCharles Gorenstein Attorney, Agent, or FirmAlbert P. Davis; Burnett W. Norton [57] ABSTRACT A novel process and apparatus for twisting filamentary material such as yarn is disclosed wherein yarn is twisted down stream of a heating means and intermediate of take-up and feed stations. Opposite sides of the yarn are contacted at successive points therealong thus gripping the yarn while both an advancing and rolling motion is imparted thereto. Such motion is imparted to the yarn in one physical embodiment of the invention by means of a pair of rolls provided with meshed teeth formed along circumferential surfaces thereof. The rolls in such embodiment are mounted in angular relationship to each other so as to permit the teeth of respective rolls to engage opposite sides of a filamentary piece of material passing between said rolls at opposite sides and at successive points therealong. Such contact along successive opposite portions of the yarn causes the yarn to take a continuous and essentially stable path between the rolls and enables a positive grip to be imparted to the yarn thereby overcoming the torque imparted to the yarn as a frictional twist component of the meshed teeth. The apparatus of the present invention may thus be characterized as a friction twist head and its method of operation a process for imparting false twist to filamentary material by frictional contact.

13 Claims, 10 Drawing Figures PATENTEB "31221974 3.842.582 sum. 11! 4 APPARATUS AND PROCESS FOR IMPARTING TWIST TO FILAMENTARY MATERIAL BACKGROUND OF THE INVENTION Various methods and apparatus for imparting false twist to filamentary material are known. As is well known, there are three basic methods for false twisting a strand of yarn: pin spindle twisting, friction twisting and fluid twisting each with its accompanying limitations and problems. In pin twisting a pin is inserted in a bearing or wheel supported hollow shaft. The strand to be twisted enters the hollow shaft, is wrapped around said pin and leaves the hollow shaft (one spindle revolution one turn on the strand). Friction twisting in its commercial form involves an element generally in the shape of a donut mounted in a false twist spindle capable of rotation about its longitudinal axis. The element engages a strand of yarn and imparts a plurality of turns of twist to the yarn for each revolution of the spindle. In fluid twisting by high velocity fluid or gas streams a strand of yarn enters a small chamber, high velocity gas is injected into this chamber to produce a high-speed rotating gas stream which imparts twist to the yarn. Such prior devices have presented increasing problems especially at the high yarn speeds needed for economic yarn processing. For example it is recognized that the speed at which yarn may be processed by pin twisting is dependent upon the speed of the twist head. Twist heads which are commercially available require extremely high rotational speeds and thus place undue strain upon bearing capacities in order to achieve such commercialy acceptable operational speeds of processed yarn. Thus if it were desired to impart 100 twists per inch (TPl) to a yarn travelling at 500 yards per minute it would be necessary to rotate the spindle at 1,800,000 RPM. Such speeds are not presently achievable and even those speeds now achievable in the range of 200,000 to 500,000 RPM impart high bearing strain with resultant undesirably high replacement costs. Fluid twisting is generally costly due to gas (air) consumption and is prone to irregularity in yarn uniformlty.

While certain successes have been achieved in the friction twisting area, e.g., the device disclosed in US. Pat. No. 3,668,856 issued June 13, 1972 to Hans H. Richter and assigned to the present assignee, Leesona Corporation, here too high commercial yarn speeds present operational criticalities. Thus will all such known friction twisters the friction elements themselves are subject to critical surface parameters which are in turn inherently subject to change by the required periodic and almost constant slippage of the yarn thereacross. Such slippage in turn causes frictional wear which further changes the surface characteristics of an element in time.

Therefore, it has been highly desirable to provide a twist device which itself operates at low speeds while capable of imparting a high twist to yarns running at commercially acceptable high yarn speeds. Representative of one such attempt in the prior art is a device disclosed in US. Pat. No. 2,943,433 to Van Dijk. This patentee discloses a pair of rollers in the form of hyperboloids disposed in mutual surface contact with each other and whereby twist is imparted to filamentary material running therebetween.. The device disclosed in this patent was never commercialized due to its impracticality because of the tolerances required to keep the mating hyperbolicv surfaces in either non abrasive contact with each other or separated from each other by an exact distance equal to the yarn thickness. This impracticality is believed even more readily apparent considering the minor thicknesses of the highly commercial fine denier yarns, e.g., those of 0.002 inch in thickness.

Other attempts which are not entirely satisfactory are represented by those devices disclosed in US. Pat. Nos. 3,045,416, 3,327,461, 3,327,463, 3,635,008, 2,908,133, 3,228,181, 3,495,390, and British Pat. No. 1,083,052. One commercially utilized friction twisting device is disclosed in US. Pat. Nos. 2,936,537 and 2,935,670 and may best be described as the donut style of friction spindle wherein yarn crosses the frictional surface at an angle and accordingly requires a relatively high frictional contact between the rotating surface and the yarn. This in turn causes the need for a relatively high tension between the rotating frictional material and the yarn which is in conflict with an inherent need for low tension in the heating zone so that the yarn may contract and shrink. Also, as previously indicated the higher the tension the more wear is imparted to the donut or other frictional surface and operational experience has shown thet the yarn may develop heat and actually cut the ring surface due to the necessary continual slippage in the axial direction. The friction generated of course depends upon the surface of the donut wherein surfaces of low durometer would tend to result in higher operational friction contact but lower wear qualities and surfaces of high durometer tending to achieve higher wear characteristics but resulting in lower operational frictional contact.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to impart a relatively high twist to yarn being processed at commercial speeds wherein the yarn does not slip axially in relationship to the friction imparting moving surface thereby avoiding the wear characteristics of the prior art devices, e.g., donuts, and resulting in friction imparting devices having greatly increased commercial life. This and other objects of the present invention are accomplished by frictionally contacting opposite sides of yarn material at successive points therealong to obtain a positive grasping of the yarn while simultaneously driving said yarn at commercial speeds and imparting acceptable twist thereto.

Accordingly, the disclosed invention avoids the abovementioned disadvantages and comprises methods and apparatus for imparting false twist to a running textile strand by combining a twist and feeding action into one single unit. The feeding action results in no significant slippage between multiple twisting and feeding elements and the strand of yarn, since both the feed and twist components are simultaneously utilized and act upon the yarn to grip the same. The twisting friction elements preferably move at a speed wherein the feed and twist components thereof are respectively matched with the yarn speed and the twist level desired. Furthermore, the multiple grip of the friction twisting elements avoids slippage between the strand and the friction elements in a direction perpendicular to the running strand. This results in a constant twist level, independent of the yarn speed, a constant tension, independent of the yarn speed, and a minimum amount of wear on the friction-feeding elements.

The accompanying drawings are illustrative of the invention:

FIG. I is a perspective view of one embodiment of the present invention utilizing opposed rollers and including an illustrative means for rotating such rollers in relationship to each other,

FIG. 2 is a cross-sectional view on an enlarged scale taken along the lines 2-2 in FIG. 1.

FIG. 3 is a partial sectional view taken along a plane intersecting the yarn path between the rollers and depicting in particular the relationship and effect of the roller teeth upon the yarn.

FIG. 4 is a partial sectional view similar to FIG. 3 but emphasises the parallel mating of the teeth of hyper bolic rolls.

FIG. 5 is a schematic showing of a portion of yarn being processed by the apparatus of the rresent invention and shows in particular the forces imparted thereto by the rolling action of the yarn contacting members.

F IG. 6 is a schematic diagram of a false twist machine in which the friction spindle of the present invention has utility.

FIG. 7 is a schematic showing of the vector forces imparted to the yarn as it is processed by the present invention.

FIG. 8 is an enlarged schematic showing of the vector forces imparted by a single yarn engaging member for a finite time increment and shown the relative distances travelled by the yarn (1-2) and the member (1-2) in that time increment.

FIG. 9 is a fragmentary plan view of an embodiment of the present invention utilizing opposed endless belts wherein the direction of travel of such belts and the yarn driven thereby are shown by the respective arrows.

FIG. 10 is a fragmentary crosssectional view on an enlarged scale of FIG. 9 taken along the yarn path.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to the drawings and particularly FIG. 1 thereof, one particular physical embodiment of the present invention is shown. Therein a friction spindle 10 is depicted and in part is comprised of rolls 12 and 12' of essentially similar construction and arranged in cooperative relationship with each other so as to provide friction twisting contact with a yarn passed therebetween in a manner which will be more clearly hereinafter brought out. Each roll 12 and 12' is comprised of a cylindrical shell 14 provided with a series of upstanding teeth 16 of the outer surface thereof. The teeth 16 are disposed parallel to each other and in the particular embodiment shown at a 45 angle to the longitudinal outer surface of the rolls l2 and 12'. Such teeth 16 terminate at either end thereof in a butting relationship to a flange member 18 mounted on opposite ends thereof.

The surface of the teeth 16 are machined or otherwise formed so as to present a helical surface contour. The upper portion of the teeth 16 are further provided with members 20 formed of material such as rubber suitable for engagement with portions of yarn passing thereacross. Such members 20 may be snap engaged into grooves (not shown) provided in the outer surfaces of the teeth 16 or may be otherwise connected thereto as by adhesive means.

Referring now to FIG. 2 of the drawing the disposition of the rolls to each other is best shown as the teeth 16 are disposed at a 45 angle across the face of the rolls 12 and 12, the further disposition of the axes of such rolls 12 and 12 at a angle to each other will place those teeth of the rolls l2 and 12' which are opposed to each other in parallel interdigital relation, when the rolls are synchronously driven at the same surface speeds. The angle of disposition of rolls to each other being determined by the general formula minus 2 .1: wherein x is the angle at which the teeth are disposed to the rolls.

The rolls are also mounted as will hereinafter be apparent so that the yarn engaging members 20 at their points of closest opposition to each other are separated by a distance at least equal to and preferably greater than the yarn thickness being processed. While it should be brought out that the opposed teeth are exact parallel relation only at the point of intersection between the central planes of the rolls, teeth portions removed and teeth adjacent such point approximate such parallel positioning and thus enable interdigertation of opposed teeth with each other so that a yarn 22 directed in a path between and normal to such teeth will be engaged by a plurality of members 20 at spaced points on opposite sides thereof. It will be thus apparent the teeth of the rolls do not pinch the yarn 22 but rather engage and roll the yarn so as to impart a twist thereto. In addition to the twist component, an anditional forward motion component is imparted ot the yarn and may serve to drive the yarn through the twisting device of the present invention.

The motion components imparted to the yarn Y are illustrated by FIG. 5 of the drawings wherein the twist component is represented by the letter T and forward motion component by the letter F. The relative amount of twist and forward motion components imparted to any particular yam Y is dependent upon the angular disposition (angle 0) of the meshed members in regard to their driving supports, e.g., rolls l2, 12, or belts (not shown) which in turn determines the relation of the yarn path to such motion imparting driving supports. This angle is the helix angle of the teeth when the driving supports are the helical gears shown in FIG. 2 of the drawings.

Inasmuch as the yarn is fed substantially at right angles to the face of the meshed members the motion components imparted to the yarn by the members of each driving support are defined by the sine and cosine of this angle as illustrated in FIGS. 7 and 8 of the drawings wherein the solid and phantom lines of FIG. 7 respectively represent upper and lower driving supports and particularly from FIG. 8 wherein the forces imparted to the yarn are shown in more detail. Thus the feed component of a tooth intersecting the axis of the driving support (wheel as illustrated) at an angle 6 is equal to (F=P cos 6) wherein F equals the axial movement of yarn (Feed) and P equals the movement of the tooth contact point in a given time increment and the twist component equal to (T=P sin 6) where T equals the circumferential movement of the yarn (Twist). It may be further seen that the number of turns imparted to the yarn is equal to T/C where C equals the circumference of the twisted yarn and that the number of turns per inch of twisted yarn (TPI) is equal to (TPI=[T/C] [l/F]) which in turn equals (TPI=tan 0/ C Thus the throretical TPl for a yarn having a diameter of 0.003 inches and angle 0 of 60 would be 184 while members disposed at the same angle would produce a theoretical TPI of 98 with yarn having a 0.0056 inch diameter.

Inasmuch as the yarn path through the supports assumes a somewhat sinuous path by reason of its contact on opposite sides and at spaced locations thereof by the yarn contacting members, an incremental greater yarn length in this path approximately is believed to exist and thus the number of twists must accordingly be spread out over a larger actual yarn length and thus reduces the theoretical TPI. The corrected theoretical TPI for the above examples then becomes 169 and 89 respectively.

Turning now to the means by which the rolls l2 and 12 may be mounted in relation to each other, each roll 12 and 12' is provided internally with a web member 24 having a central opening 26 therethrough for receipt of an upstanding boss 28 in turn connected to a shaft 30 supported for rotation in housing 32 by means of a gear 34 mounted on the bottom end thereof. Such gear 34 meshes with gear 36 which in turn is driven through shaft 38 by means of a belt 40. The belt 40 in turn is connected to means (not shown) for rotating the shaft 41 of the roller 12' at the same speed and in a similar manner to the rotation of the previous roller 12. The direction of rotation of both rollers is indicated in FIG. 1 of the drawings which enable the opposed teeth of such rollers 12 to interdigitate in the manner above described.

As best shown in FIG. 6, yarn 22 to be processed is fed from a supply 44 through guide 46 by means of feed rolls 48 through a heater 50 to the spindle 10 where twist is imparted thereto and then through take up rolls 52 to a take up package 54. Except for the subject spindle 10 this overall process is well known in the art and essentially involves the use of the lower feed rolls as a twist stop so that twist imparted to the yarn between these rolls and the spindle is permitted to build up by reason of the softening effect thereon in the heater and is thereafter fixed or set by the action of a cooling zone located between the spindle and the heater as the twisted yarn emerges from the heater. The spindle 10 of the present invention imparts twist to the yarn 22 as it passes from the heater and is thereafter guided normally across the meshed teeth 16 of rolls l2 and 12' by means of guides 42, in a diagonal path normal to the teeth from the lower left side to the upper right side of the upright roll as shown in FIG. 1 of the drawings.

Such twist and forward motion components imparted to the yarn by the subject process is illustrated in FIG. 5 of the drawings wherein Y represents a segment of yarn at the approximate midpoint of coaction between opposed teeth 16 and T the twist or rolling force component imparted thereto and F the forward or linear motion component thereof. Inasmuch as the yarn engaging surfaces or members of the interdigitating teeth 16 do not pinch but roll the yarn and since the yarn is engaged at a plurality of spaced locations on opposite sides thereof, the yarn in effect becomes positively grasped or gripped and twist is imparted thereto by the above described rolling action as the yarn is simultaneously moved linearly through the processing zone. Such action is believed to be enhanced by reason of the greater degree of wrap of the yarn over the contacting members brought about by reason of the interdigitation of such members. Such positive grasping of the yarn enables the twist device of the present process to itself operate at low speeds while imparting high twist to yarns running at commercially acceptable high yarn speeds since it is not necessary as in prior art friction twisting devices to overdrive the engaging surface far in excess of theoretical values due to the high degree of slippage present in such devices and inherently necessary for operation of such devices. The present friction spindle imparts twist to the yarn without necessitating slip between the yarn and its contacting surface and thus to a great part additionally eliminate slippage and the attendent wear slippage causes upon the yarn contacting surfaces of prior art devices. The present device thus provides resultant twist at values approaching theoretical values determined from the analysis of the forces imparted thereto in distinct contrast to prior art friction twisters (bushing or donut style) where slippage between the yam is inherent and wherein all kinds of added factors such as yarn finish and tension affect the resultant twist lever.

While the friction spindle of the present invention may be utilized to itself feed yarn in addition to its twisting action, such feed ability is not necessary when used with commercially available false twist equipment since yarn feed and take up means are already provided thereon and thus serve to feed and tension the yarn being processed. However it is preferable to coordinate the spindle speeds with those of the feed and take up rolls so that the axial forces imparted to the yarn approximate the actual axial direction speed imparted thereto by the feed and take up rolls.

Two rolls similar to those shown in the drawings and having helix angles of 45 were mounted as herein described and operated to twist yarn being processed in a Leesona Model No. 570 false twist texturing machine. The results are as follows:

(in twisted condition) What is claimed is:

1. Apparatus for imparting twist to filamentary mate rial comprising:

a pair of members,

each of said members provided with parallel projections along a surface thereof,

a section of each of said member surfaces adjacent to and in partial overlapping relationship to each other to define an area of overlap between said member surfaces whereby projections of each member are in meshed interdigitative relationship with each other within a portion of said overlapping area, said projections being spaced apart from each other at their points of closest opposition by a distance at least equal to the thickness of said filamentary material, said portion defining a zone of filamentary contact, and

a plurality of said projections contacting said filamentary material at spaced location on opposite sides thereof within said zone,

means for directing filamentary material across said projections and generally normal thereto within said zone and means for moving said member surfaces through said zone, said member surfaces further being disposed to each other so that planes respectively disposed normal to the direction of travel of each said member surface through said zone are disposed in non-parallel angular relationship to each other and the projections of each of said members in angular relation to the respective plane normal to the direction of travel of the surface of its respective memher.

2. The apparatus of claim 1 wherein said projections are equidistant and including means driving said members at equal surface speeds.

3. The apparatus of claim 1 wherein said members are rolls.

4. The apparatus of claim 1 wherein said members are belts.

5. Apparatus of claim 1 wherein the surface of each said projection is hyperbolic.

6. Apparatus for imparting twist to filamentary material comprising a pair of rolls, said rolls mounted with the longitudinal axis of each roll in non-parallel angular relationship to each other, the circumferential surface of each of said rolls provided with equidistant parallel teeth projecting therefrom and in angular relation to the axis of each said roll, the teeth of one said roll meshed in non contacting relationship with the teeth of the other of said rolls, said teeth being spaced apart from each other at their points of closest opposition by a distance slightly greater than the thickness of said filamentary material means for directing filamentary material across said teeth and generally normal thereto a plurality of said teeth contacting said filamentary material at spaced locations on opposite sides thereof,

and means for driving said rolls at equal surface speeds.

7. Apparatus of claim 6 wherein said teeth are equiangularly disposed in relation to said rolls.

8. A process for imparting twist to filamentary material comprising directing said filamentary material into a zone comprising opposed surfaces spaced apart from each other at their points of closest opposition by a distance slightly greater than the thickness of said filamentary material,

contacting said filamentary material in said zone solely at a plurality of spaced locations on opposite sides thereof,

and rolling said filamentary material by contact with said opposed surfaces to simultaneously impart circumferential and axial direction force components thereto so as to simultaneously advance said filamentary material through said zone while imparting twist thereto.

9. The process of claim 8 wherein the path of said filamentary material in said zone is sinuous.

10. The process of claim 8 wherein said opposed surfaces are in meshed interdigitive relationship to each other during contact with said filamentary material.

11. The process of claim 8 wherein said opposed surfaces are in meshed interdigitive relationship to each other in said zone and wherein said surfaces cumulatively grip said filamentary material.

12. The process of claim 11 wherein said filamentary material is fed to said zone by feed and take-up means respectively upstream and downstream of said zone at a first rate and wherein said first rate is greater than the advancement rate imparted by said axial force component but not great enough to cause frictional slip between said filamentary material and said surfaces.

13. The process of claim 8 wherein said filamentary material is fed to said zone by feed and take-up means respectively upstream and downstream of said zone at a first rate and wherein the advancement rate said axial force component imparts to said filamentary material in said zone is substantially equal to said first rate. 

1. Apparatus for imparting twist to filamentary material comprising: a pair of members, each of said members provided with parallel projections along a surface thereof, a section of each of said member surfaces adjacent to and in partial overlapping relationship to each other to define an area of overlap between said member surfaces whereby projections of each member are in meshed interdigitative relationship with each other within a portion of said overlapping area, said projections being spaced apart from each other at their points of closest opposition by a distance at least equal to the thickness of said filamentary material, said portion defining a zone of filamentary contact, and a plurality of said projections contacting said filamentary material at spaced location on opposite sides thereof within said zone, means for directing filamentary material across said projections and generally normal thereto within said zone and means for moving said member surfaces through said zone, said member surfaces further being disposed to each other so that planes respectively disposed normal to the direction of travel of each said member surface through said zone are disposed in nonparallel angular relationship to each other and the projections of each of said members in angular relation to the respective plane normal to the direction of travel of the surface of its respective member.
 2. The apparatus of claim 1 wherein said projections are equidistant and including means driving said members at equal surface speeds.
 3. The apparatus of claim 1 wherein said members are rolls.
 4. The apparatus of claim 1 wherein said members are belts.
 5. Apparatus of claim 1 wherein the surface of each said projection is hyperbolic.
 6. Apparatus for imparting twist to filamentary material comprising a pair of rolls, said rolls mounted with the longitudinal axis of each roll in non-parallel angular relationship to each other, the circumferential surface of each of said rolls provided with equidistant parallel teeth projecting therefrom and in angular relation to the axis of each said roll, thE teeth of one said roll meshed in non contacting relationship with the teeth of the other of said rolls, said teeth being spaced apart from each other at their points of closest opposition by a distance slightly greater than the thickness of said filamentary material means for directing filamentary material across said teeth and generally normal thereto a plurality of said teeth contacting said filamentary material at spaced locations on opposite sides thereof, and means for driving said rolls at equal surface speeds.
 7. Apparatus of claim 6 wherein said teeth are equiangularly disposed in relation to said rolls.
 8. A process for imparting twist to filamentary material comprising directing said filamentary material into a zone comprising opposed surfaces spaced apart from each other at their points of closest opposition by a distance slightly greater than the thickness of said filamentary material, contacting said filamentary material in said zone solely at a plurality of spaced locations on opposite sides thereof, and rolling said filamentary material by contact with said opposed surfaces to simultaneously impart circumferential and axial direction force components thereto so as to simultaneously advance said filamentary material through said zone while imparting twist thereto.
 9. The process of claim 8 wherein the path of said filamentary material in said zone is sinuous.
 10. The process of claim 8 wherein said opposed surfaces are in meshed interdigitive relationship to each other during contact with said filamentary material.
 11. The process of claim 8 wherein said opposed surfaces are in meshed interdigitive relationship to each other in said zone and wherein said surfaces cumulatively grip said filamentary material.
 12. The process of claim 11 wherein said filamentary material is fed to said zone by feed and take-up means respectively upstream and downstream of said zone at a first rate and wherein said first rate is greater than the advancement rate imparted by said axial force component but not great enough to cause frictional slip between said filamentary material and said surfaces.
 13. The process of claim 8 wherein said filamentary material is fed to said zone by feed and take-up means respectively upstream and downstream of said zone at a first rate and wherein the advancement rate said axial force component imparts to said filamentary material in said zone is substantially equal to said first rate. 